Hi Paul! You are off to a great start! A few things -- and fair warning, I'm nit-picking as you asked
WHITE BALANCE -- Get an
18% grey card to calibrate your shots. Depending on what software you are using for post-production, you only need to adjust this once and then you can batch apply it to your whole session. I leave calibration cards up on my shooting environment for the whole session (along with rulers), which makes it easy to dial this in quickly. If you have a grey card visible in your shot, it's a one-click fix to dial in white balance in most software programs.
WHITE BALANCE -- Another white balance tip, use the same kind of light. Meaning don't mix strobes with daylight, fluorescents, incandescents, etc... stick to one kind of light source. Given you have strobes, you should try to eliminate all other light sources. That means cover those windows, and only use a few other lights in the room (placed to the sides) to work by. If you strobes can over power them, you are good to go. To test this, dial in your setup with the strobes, ensuring the poster is properly lit (do you have a light meter?). Then turn them off and shoot another test shot. If it comes out all black your dim room lights shouldn't affecting your lighting setup, but they will still give you some light to work with while shooting and changing posters. If you are shooting in some sort of "auto" mode this test will probably not work. Just record the settings from the auto mode (ISO, aperture, shutter speed), switch to manual (M) mode and enter those settings. Take a test shot to ensure the lighting is still correct, then proceed with turning off the strobes and testing your room lighting/reflections.
REFLECTIONS -- Again, cover those windows! You don't want any stray light reaching your lens. Anything behind the poster is a definite no-no, as are light sources behind the camera -- those will reflect off the poster (your metal board, the white wall, etc...) on to the lens as well.
REFLECTIONS -- You can also get a cheap lens hood to kill stray light coming from the sides -- including the light coming from the strobes. You want to poster to be lit, not the lens.
REFLECTIONS -- Reverse roll your posters for a few days before shooting. This will help eliminate those pesky curls that cast shadows and add reflections. Basically, you only want to be shooting pre-flatted posters. I try to group posters by size -- meaning I will shoot a session of only B2s. Then another session I'll only do 1-sheets. That makes your setup and post production more straight-forward, but it also allows me to establish a kind of queue. I always prep for the next session by pre-flattening.
DISTORTION -- I could be seeing things, but it looks like you might have a bit of
barrel distortion. What focal length are you using? It looks like you might be using a wider lens, which can lead to slight distortion in the image. The farther back you can get the camera the less distortion you'll see and, as a bonus, the more it will help with combating stray light and reflections. If you are using an camera with an APS-C sized sensor (I think you are) I would use something at least 35mm (50mm equiv. to full-frame), or if possible 60mm (90mm equivalent).
SHARPNESS -- Entry level lenses are usually not known for the optical precision. Better/costlier lenses
should be sharp all the way into the extreme corners. You can help your sharpness by using a higher F-stop -- for APS-C I would recommend F8. If you are still getting blurry corners, you can just move your camera back a bit more and then crop out the extra space. For the web, your photos will likely only be 2-3000 pixels on the long side. If you choose 3000x2250 that works out to about a 7mp image. If you are shooting with a 12-16mp camera that means you can setup your shooting environment with the expectation of cropping down to 7mp -- and also cropping out those soft corners from entry-level lenses.
That's probably enough for now... I'll try to contribute more tips as I think of them. Great work!
